1. Field of the Invention
The present invention relates to a liquid transporting apparatus which transports an electroconductive liquid.
2. Description of the Related Art
A recording head of an ink-jet type which jets an ink from nozzles onto a recording medium is generally used for a printer which records an image or the like by discharging (jetting) an ink onto a recording medium such as a recording paper. In such a recording head of the ink-jet type, however, the structure of an ink channel in the recording head and the structure of an actuator which generates a jetting pressure to be applied to the ink become special and complicated. Therefore, it has been difficult to minitualize the recording head by arranging a plurality of nozzles highly densely.
In view of this, the inventor of the present invention has proposed a new type of a recording head which uses, in a case that a surface of an electrode is covered by an insulating layer, a phenomenon (electrowetting phenomenon) in which a liquid repellent property (wetting angle) is changed on a surface of the insulating layer when an electric potential difference is changed between an electric potential of the surface of the insulating layer and an electric potential of the electrode (for example, see US Patent Application Publication No. US2005/219330 (corresponding to Japanese Patent Application Laid-open No. 2005-288875)). This recording head includes a plurality of individual channels formed as a plurality of grooves. Further, an individual electrode is provided to a channel-forming surface of each of the individual channels (bottom surface of each of the grooves); and in each of the individual channels, the surface of the individual electrode is covered by the insulating layer. Furthermore, since an ink in the head is in contact with a common electrode which is kept at a ground electric potential, an electric potential of the ink is always maintained at the ground electric potential. Moreover, at an upstream side of the individual channels, there is provided a pump which pressurizes the ink toward a discharge section formed in each of the individual channels at a front end (downstream end) thereof.
Here, an electric potential of the individual electrode is the ground electric potential, and when there is no electric potential difference between the ink and the individual electrode, then the liquid repellent property (wetting angle) on the surface of the insulating layer at a portion thereof sandwiched between the ink and the individual electrode is higher than a liquid repellent property on the surface of the insulating layer at an area thereof in which the insulating layer of a groove bottom surface is not provided or partially absent. Therefore, the ink cannot flow (cross) over or across the surface of the insulating layer to the discharge section, and thus the ink is not discharged from the discharge section. On the other hand, when the electric potential of the individual electrode is a predetermined electric potential which is different from the ground electric potential, there arises an electric potential difference between the ink and the individual electrode, and the liquid repellent property (wetting angle) is lowered on the surface of the insulating layer at the portion thereof sandwiched between the ink and the individual electrode (electrowetting phenomenon). As a results, the ink pressurized by the pump become movable to the discharge section while wetting the surface of the insulating layer, and the ink is discharged from the discharge section.